Moved transformation argument validation to the model

apps/sources/models.py

@@ -1,7 +1,10 @@
+from ast import literal_eval
+
 from django.db import models
 from django.utils.translation import ugettext_lazy as _
 from django.contrib.contenttypes.models import ContentType
 from django.contrib.contenttypes import generic
+from django.core.exceptions import ValidationError
 
 from documents.models import DocumentType
 from metadata.models import MetadataType
@@ -105,6 +108,27 @@ class WebForm(InteractiveBaseModel):
         verbose_name_plural = _(u'web forms')
 
 
+class ArgumentsValidator(object):
+    message = _(u'Enter a valid value.')
+    code = 'invalid'
+
+    def __init__(self, message=None, code=None):
+        if message is not None:
+            self.message = message
+        if code is not None:
+            self.code = code
+
+    def __call__(self, value):
+        """
+        Validates that the input evaluates correctly.
+        """
+        value = value.strip()
+        try:
+            literal_eval(value)
+        except (ValueError, SyntaxError):
+            raise ValidationError(self.message, code=self.code)
+
+
 class SourceTransformation(models.Model):
     """
     Model that stores the transformation and transformation arguments
@@ -115,7 +139,7 @@ class SourceTransformation(models.Model):
     content_object = generic.GenericForeignKey('content_type', 'object_id')
     order = models.PositiveIntegerField(default=0, blank=True, null=True, verbose_name=_(u'order'), db_index=True)
     transformation = models.CharField(choices=get_available_transformations_choices(), max_length=128, verbose_name=_(u'transformation'))
-    arguments = models.TextField(blank=True, null=True, verbose_name=_(u'arguments'), help_text=_(u'Use dictionaries to indentify arguments, example: %s') % u'{\'degrees\':90}')
+    arguments = models.TextField(blank=True, null=True, verbose_name=_(u'arguments'), help_text=_(u'Use dictionaries to indentify arguments, example: %s') % u'{\'degrees\':90}', validators=[ArgumentsValidator()])
 
     objects = SourceTransformationManager()